1. Field of the Invention
The present invention relates to an electrode of copper-based sintered alloy for use in an ignition distributor of an internal combustion engine, and in particular to an improved electrode which exhibits low capacitive-discharge current peaks and discharge starting voltages, thereby preventing radio wave noise from being generated.
2. Prior Art
Generally, in a known ignition distributor of an internal combustion engine, a high voltage stored in an ignition coil is transferred through a high voltage cable from a central terminal and led through a spring and a carbon electrode to a rotor electrode, to cause dielectric breakdown of air in the discharging gap between the tip end of the rotor electrode and each side fixed electrode, whereby the high voltage is discharged to the side fixed electrodes. The high voltage thus distributed is further led to spark plugs through high voltage cables. The aforesaid rotor electrode has conventionally been made of brass or stainless steel, while the side fixed electrodes have usually been made of aluminum.
Furthermore, it has been hitherto known that in the ignition distributor of an internal combustion engine as described above, radio wave noise is generated due to the current discharged between the rotor electrode and the side fixed electrode, and this disrupts radio broadcasts, television broadcasts and other communications. In order to prevent the generation of the radio wave noise, various kinds of electrodes have hitherto been proposed, as disclosed, for example, in Japanese Patent Application B-Publication, Serial No. 51-38852; Japanese Patent Application A-Publication, Serial No. 55-78173; and Japanese Patent Application B-Publication, Serial No. 58-28427.
However, all of the prior art electrodes have been constructed so as to have insulating layers on their surfaces, and these layers are susceptible to separation. This problem of separation has especially been encountered in the case where the ignition distributor is made large in size or is improved so as to have superior performance. Thus, the prior art electrodes had drawbacks in their reliabilities.